The wettability of a surface can be an extremely useful property. For example, hydrophilic surfaces are advantageous in a variety of biomedical, anti-fogging, and heat transfer applications, and hydrophobic surfaces are used in self-cleaning applications.
Wettability is determined by a combination of the chemical composition and the topography of a surface. Chemical interactions at solid-liquid-vapor interfaces determine the interfacial free energy, which in turn determines whether the surface is hydrophilic or hydrophobic. The role of topography is less well understood, but it is well known that roughness amplifies the intrinsic wetting characteristics of a material. This phenomenon has been used to create superhydrophilic and superhydrophobic surfaces.